During the past four decades, extensive research has been carried out on different noise barrier shapes using analytical and physical modelling as well as full scale testing. This paper reviews traffic noise barrier research and its findings to date. It provides a catalogue of noise barrier profiles; identifying the relative acoustic benefits of each and the physical principles on which they operate. The likely effects of ground and atmospheric conditions on their absolute acoustic performance are described. The types of barriers which are commonly used in practice and those deserving further attention are highlighted. Based on the findings of previous work, recommendations are made on possible areas of further research.
This research programme is concerned with the design of road traffic noise barriers, in particular, the use of multiple-walls on the ground and on top of earth mound type barriers. As part of this research, a comprehensive up-to-date review of the research carried out on noise barriers was undertaken. A number of areas requiring further research were identified. The discussion of these resulted in the proposal of a simplified noise barrier selection method which would be of use particularly to non-acousticians. This method indicated that acoustic information available for the design of earth mounds was limited, although this barrier type is commonly used in practice and is known to have a number of non-acoustic benefits. Initial investigations showed that the performance of an earth mound could be enhanced by the use of multiple-walls on its top. A detailed investigation was undertaken into the acoustic performance of multiple-walls both on the ground and on top of earth mounds. Both physical and numerical modelling techniques were used for this purpose. The physical scale modelling experiments were carried out both under uniform field conditions and in two different semi-anechoic chambers in the presence of a continuous noise source, using a model scale of 1: 10. The numerical modelling was applied using indirect boundary element method formulation. The commercial software named SYSNOISE was employed for the computations. It was found that numerical modelling results and the semi-anechoic chamber experiments generally agreed very well. The level of accuracy of the uniform field experiments depended on the choice of source and receiver locations as well as the size of the model geometry. This investigation resulted in acoustic advice on the use of multiple walls both on their own and on top of earth mounds. Under favourable conditions, the multiple-wall configurations were shown to provide substantial attenuations of up to 26dB. The physical parameters involved in their design and their noise attenuation mechanisms were identified. In addition to long-wave scattering and diffraction effects, it was identified that surface wave generation mechanisms and interference effects played a role in attenuating noise. The acoustic advice for the design of earth mounds was extended to the applications of single, double and multiple-walls on their top. This work also showed that uniform field conditions in conjunction with a continuous noise source could be used for physical modelling. It was found that for small-sized geometries good agreements were observed between physical modelling (both types) and numerical simulations. There were lesser agreements between the sets of data for larger geometries. The multiple-wall configurations investigated as part of this research programme could be used as noise mitigating measures in central reservations of dual carriageways. However, further research would be required into their acoustic performance and engineering design. The results obtained from this investigation have led to the identification of a number of research areas which could be undertaken in the future.
This paper investigates the use of periodically spaced edges or wells for the control of road traffic noise. The wells have uniform height and width and are placed on the ground. Physical scale modeling is used to assess the acoustic performance of these structures under laboratory conditions. It is shown that, in certain situations where the use of conventional barriers would not be appropriate, strategically designed riblike structures can provide insertion losses of typically 10-15 dB. The findings are explained in terms of acoustic scattering with the approaches used in the study of resonators and diffraction/interference gratings.
Design and constnrction of environmental barriers requires the involvement of specialists from many disciplines.In addition to acousticians.architects, planners.landscape architects.civil engineers, highway engineers.stnrctural engineers and gen-technical engineers.the community must also be involved for an effective and
Despite an increase in the number of complaints about environmental noise, action to reduce its impact has had a lower priority compared to other environmental problems. According to the European Commission Green Paper on Future Noise Policy, around 20% of the European Union's population or 80 million people suffer from noise levels more than 65 dB(A). These levels are considered by health experts to be unacceptable. As well as enviromnental implications noise has economic costs to society. This paper presents some of the work being carried out on a novel method of screening road traffic noise consisting of earth mounds combined with short barriers. Physical scale modelling was used to measure the performance of eight different configurations. A sample of the results is presented and discussed. For the covering abstract see ITRD E107776.
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